Global Positioning Systems (GPS), or GPS receivers, are being used in increasing numbers in automobiles to provide vehicle navigation functions. Typically, a GPS receiver or navigation device comprises a digital road map, or geographic information (GIS) database, of the area of travel. A user, such as the driver of a vehicle, inputs a destination into the GPS navigation device and the GPS navigation device calculates a route from the current position of vehicle, through the network of roads as represented in the GIS database, to the destination. Turn-by-turn directions are relayed to the driver through visual or audible prompts. The current position of the vehicle is determined by receiving GPS signals from GPS satellites. If the GPS signals are obstructed or interfered with, the current position of the vehicle may be very difficult to ascertain and the usefulness of the GPS navigation device is severely degraded. GPS signals may be obstructed, for example in urban areas with many tall buildings, on roads with many trees or mountains, and in areas with high levels of background radio noise or interference.
In order to provide accurate driving direction the GIS database must be kept current and up-to-date. Databases, with varying levels of accuracy, are commercially available and are released for purchase and installation into GPS receivers at regular intervals. Oftentimes, since the databases are updated manually through visual surveys of the roadways, aerial observations, government data, and individual travel on the roadways, it takes on average six months to create a new database. Additionally, on average, by the time a user is able to obtain the database and install it the database is already obsolete by around three months. Furthermore, the database is only as good as the individual observations and therefore may be incomplete in certain areas of travel as observations have not been made of those areas.
Some attempts have been made to automate the database update process by providing a central database and a plurality of vehicles containing sensors. The vehicles travel a geographical region of interest and collect sensor information. The sensor information is processed and communicated to the central database. The central database receives the sensor information, processes it further, and integrates the sensor information into the central database. The centralized-only communication architecture of these approaches increases the cost and complexity of integrating the collected data. Furthermore, these approaches require a large number of vehicles constantly moving around the geographic region in order to cover as much area as possible, and collect as much sensor information as possible. Additionally, it is very difficult to collect consistent sensor measurements of an identical route since different traffic conditions, drivers, traffic lights, weather, and the like will result in different sensor measurements and thus different information pertaining to a particular route. Also, this centralized only approach relies on wireless communications directly to the central database. In many cases, due to geographical considerations for example, it may not be possible to communicate at all with the central database.
It would be advantageous to have systems and methods that communicate map databases and route information between vehicles traveling a transportation network, and between vehicles and a central database without the limitations of the prior art. It would be further advantageous to have systems and methods that determine the geographic location of vehicles unable to receive GPS signals. Thus a need presently exists for systems and methods for determining the location of a vehicle traveling a transportation network.